Some stereoscopic image viewing devices (simply referred to below as viewing devices) generally called 3D eyeglasses or 3D glasses support active system and some support passive system.
In the active system, a right-eye image and a left-eye image are displayed on a display device, such as a television, while being alternatingly switched therebetween. On the other hand, on a viewing device, liquid crystal shutters or suchlike disposed on right and left lens portions are alternatingly opened/closed in synchronization with switching of images on the display device (see Patent Literatures 1 and 2).
Display devices used with the active system are structured approximately in the same manner as conventional display devices. In addition, simply using stereoscopic image data as image data to be displayed on the display devices allows stereoscopic image viewing.
On the other hand, in the passive system, right-eye and left-eye images are simultaneously displayed line-by-line on the display device, and in the display device, a polarizing filter sorts the images for the right eye and the left eye. Then, the sorted images are respectively delivered to the right eye and the left eye through specialized eyeglasses. Accordingly, in the passive system, 3D images in some cases could not be properly viewed unless the images are viewed generally in front of the display device. Moreover, since the right-eye and left-eye images are displayed on one screen at the same time, the resolution is low. Therefore, for viewing on a household television, the active stereoscopic image viewing system is preferable for users.
However, in the active system, the viewing device is required to include liquid-crystal optical shutters and a power source for driving them, so that the viewing device becomes heavier and bulkier than normal eyeglasses. Therefore, many users feel discomfort with wearing the viewing device.
Accordingly, active stereoscopic image viewing systems are desired to have lighter viewing devices for improved comfort of wearing. Currently, it is the mainstream practice to use a small, lightweight, coin-shaped primary battery for a drive power source. Also, to achieve a lighter viewing device, it is under study to use a laminated battery as a drive power source since laminated batteries can be rendered thinner more easily than coin-shaped batteries.
Furthermore, attention is drawn by a technology in which eyeglass lenses include electroactive elements made of liquid crystals. Current to be applied to the electroactive elements is adjusted to instantaneously change the lenses' power (refractive power) or focal point (see Patent Literatures 3, 4, and 5). This technology makes it possible to achieve eyeglasses (referred to below as variable focus eyeglasses) in which the power of myopia correction eyeglass lenses can be partially changed to a power for hyperopia correction as necessary or the power for the entire field of view of eyeglass lenses can be switched between powers for myopia correction and hyperopia correction as necessary. This makes it possible to achieve a satisfactory field of view without distortion when compared to general, so-called bifocal eyeglasses or suchlike.